smc: support mini smc_run

examples/c/Makefile

@@ -24,7 +24,7 @@ INCLUDES := -I$(OUTPUT) -I../../libbpf/include/uapi -I$(dir $(VMLINUX)) -I$(LIBB
 CFLAGS := -g -Wall
 ALL_LDFLAGS := $(LDFLAGS) $(EXTRA_LDFLAGS)
 
-APPS = minimal minimal_legacy bootstrap uprobe kprobe fentry usdt sockfilter tc ksyscall task_iter
+APPS = minimal minimal_legacy bootstrap uprobe smc kprobe fentry usdt sockfilter tc ksyscall task_iter
 
 CARGO ?= $(shell which cargo)
 ifeq ($(strip $(CARGO)),)

examples/c/smc.bpf.c

@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause
+/* Copyright (c) 2021 Sartura */
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+#include <bpf/bpf_endian.h>
+
+char LICENSE[] SEC("license") = "Dual BSD/GPL";
+
+#define AF_INET         2       /* Internet IP Protocol         */
+#define AF_INET6        10
+#define IPPROTO_SMC   	263
+
+SEC("fmod_ret/update_socket_protocol")
+int BPF_PROG(smc_run, int family, int type, int protocol)
+{
+
+        if ((family == AF_INET || family == AF_INET6) &&
+            type == SOCK_STREAM &&
+            (!protocol || protocol == IPPROTO_TCP)) {
+                return IPPROTO_SMC;
+        }
+
+        return protocol;
+}

examples/c/smc.c

@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+/* Copyright (c) 2021 Sartura
+ * Based on minimal.c by Facebook */
+
+#include <stdio.h>
+#include <unistd.h>
+#include <signal.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/resource.h>
+#include <bpf/libbpf.h>
+#include "smc.skel.h"
+
+static int libbpf_print_fn(enum libbpf_print_level level, const char *format, va_list args)
+{
+	return vfprintf(stderr, format, args);
+}
+
+static volatile sig_atomic_t stop;
+
+static void sig_int(int signo)
+{
+	stop = 1;
+}
+
+int main(int argc, char **argv)
+{
+	struct smc_bpf *skel;
+	int err;
+
+	/* Set up libbpf errors and debug info callback */
+	libbpf_set_print(libbpf_print_fn);
+
+	/* Open load and verify BPF application */
+	skel = smc_bpf__open_and_load();
+	if (!skel) {
+		fprintf(stderr, "Failed to open BPF skeleton\n");
+		return 1;
+	}
+
+	/* Attach tracepoint handler */
+	err = smc_bpf__attach(skel);
+	if (err) {
+		fprintf(stderr, "Failed to attach BPF skeleton\n");
+		goto cleanup;
+	}
+
+	if (signal(SIGINT, sig_int) == SIG_ERR) {
+		fprintf(stderr, "can't set signal handler: %s\n", strerror(errno));
+		goto cleanup;
+	}
+
+	printf("Successfully started! Please run `sudo cat /sys/kernel/debug/tracing/trace_pipe` "
+	       "to see output of the BPF programs.\n");
+
+	while (!stop) {
+		fprintf(stderr, ".");
+		sleep(1);
+	}
+
+cleanup:
+	smc_bpf__destroy(skel);
+	return -err;
+}